Dendritic cells (DC) were originally identified by Ralph Steinman as bone marrow derived professional antigen presenting cells, being the only cell of the immune system capable of activating naïve T cells [1]. Subsequent studies have shown that DC act as a critical bridge between the innate immune system, which is constantly patrolling for various “danger” signals such as toll like receptor (TLR) agonists that are associated with tissue injury or pathogenic threat. In contrast to other antigen presenting cells such as the macrophage or the B cell, DC exhibit magnitudes of higher ability to stimulate T cell responses both in antigen specific systems, as well as in polyclonal experiments such as in mixed lymphocyte reaction [2]. It is known that in peripheral tissues (outside of lymph nodes), DCs capture antigens through several complementary mechanisms including phagocytosis and receptor mediated endocytosis. Immature DC are known to possess high degree of phagocytic activity and low levels of antigen presenting activity. Normally, DCs in peripheral tissues are immature. These immature DCs have the ability to efficiently capture antigens; they can accumulate MHC class II molecules in the late endosome-lysosomal compartment; they can express low levels of co-stimulatory molecules; they can express a unique set of chemokine receptors (such as CCR7) that allow their migration to lymphoid tissues; and they have a limited capacity for secreting cytokines [3].
Once DC are activated, by a stimulatory signal such as a toll like receptor agonist, phagocytic activity decreases and the DC then migrate into the draining lymph nodes through the afferent lymphatics. During the trafficking process, DC degrade ingested proteins into peptides that bind to both MHC class I molecules and MHC class II molecules. This allows the DC to: a) perform cross presentation in that they ingest exogenous antigens but present peptides in the MHC I pathway; and b) activate both CD8 (via MHC I) and CD4 (via MHC II). Interestingly, lipid antigens are processed via different pathways and are loaded onto non-classical MHC molecules of the CD1 family [4]. DCs promptly respond to environmental signals and differentiate into mature DCs that can efficiently launch immune responses. As stated above, maturation is associated with the downregulation of antigen-capture activity, the increased expression of surface MHC class II molecules and costimulatory molecules, the ability to secrete cytokines as well as the acquisition of CCR7, which allows migration of the DC into the draining lymph node. The ligation of the costimulatory receptor CD40 (also known as TNFRSF5) is an essential signal for the differentiation of immature DCs into fully mature DCs that are able to launch adaptive T cell-mediated immunity [5]. However, DC maturation alone does not result in a unique DC phenotype. Instead, the different signals that are provided by different microbes or viruses either directly or through the surrounding immune cells induce DCs to acquire distinct phenotypes that eventually contribute to different immune responses. Indeed, DC maturation varies according to different microbes because microbes express different pathogen associated molecular patterns (PAMPs) that trigger distinct DC molecular sensors, which are called pattern recognition receptors (PPRs). Strikingly, although most microbes activate DCs, a few can block DC maturation through various pathways [6]. Tissue-localized DCs can also be polarized into distinct phenotypes by the products released from surrounding immune cells that respond to injury. For example, gamma delta-T cells and NK cells release interferon-γ (IFNγ), mast cells release pre-formed IL-4 and TNF, pDCs secrete IFNa, stromal cells secrete IL-15 and thymic stromal lymphopoietin (TSLP), and so on. These cytokines induce the differentiation of progenitor cells or of precursor cells such as monocytes into distinct inflammatory DCs that yield unique types of T cells. On interaction of CD4 and CD8 T cells with DC, these cells can subsequently differentiate into antigen-specific effector T cells with different functions. CD4 T cells can become T helper 1 (TH1) cells, TH2 cells, TH17 cells or T follicular helper (T) cells that help B cells to differentiate into antibody-secreting cells, as well as Treg cells. Naive CD8 T cells can give rise to effector cytotoxic T lymphocytes (CTLs).
The utilization of NK cells and LAK cells in the context of cancer therapy has previously been used with success in numerous studies. Unfortunately this technology has never been commercialized in the veterinary setting. The current patent discloses specifics of utilizing a multiple canine cellular combination to stimulation cytotoxic cell production in an autologous manner.